The present invention relates to a disc recording medium where a specific physical format is prescribed, and also to a reproducing apparatus adapted for playing such a recording medium.
Recently, a variety of recording media and recording/reproducing apparatus are in practical use to meet requirements with advanced high-density recording media inclusive of discs and tapes, and further due to diversified data usage of audio, video and computer data.
As for disc media, there are known, relative to the CD (Compact Disc) type, CD-DA (CD Digital Audio), CD-G, CD-I, CD-WO, video CD, CD-ROM and so forth. Further, as termed CD extra, there is known a type where a CD-DA data area and a CD-ROM data area are set separately.
In addition, MD (Mini Disc) and MD data are also diffused as magneto-optical disc media which are suited for users to record and/or reproduce audio or computer data with facility.
Besides the above, DVD (Digital Video Disc/Digital Versatile Disc) is also developed as a multimedia disc which deals with video data, audio data, computer data and so forth.
In developing any novel media system such as DVD, it is demanded to solve the problems of the existing media systems already in practical use and further to inherit and extend the advantages thereof.
Out of many problems currently observed in the conventional systems known heretofore, some examples are as follows.
First with regard to digital audio data recording/reproducing systems, in comparison with the current CD-DA standards inclusive of 44.1 kHz sampling and 16-bit quantization, various higher-bit and higher-sampling digital audio recording/reproducing systems are developed in accordance with the recent trend of realizing greater capacities of media and higher transfer rates thereof. However, each of them fails to satisfy the conditions required as a next-generation audio system.
In the CD-DA standard for example, any frequency band above 22 kHz is filtered due to the limit of a sampling rate, so that higher harmonics included originally in an audio signal are cut in the data, whereby the sound quality is somewhat deteriorated with a lack of natural feeling. For this reason, an improved standard is proposed with 96 kHz sampling and 24-bit quantization, but it is still impossible to eliminate deterioration of the sound quality that results from a limit of higher harmonics.
There is also known another CD-DA system where an analog audio signal is converted by a 1-bit .DELTA..SIGMA. modulation A/D converter into a signal of sampling frequency 64 fs/1 bit (fs=44.1 kHz). However, for recording in CD-DA, such a 64 fs/1 bit signal needs to be converted into data of 44.1 kHz/16 bits through decimation (down-sampling) by a digital filter. And in a reproducing mode, the data of 44.1 kHz/16 bits is turned into, e.g., 64 fs/1 bit signal through over-sampling by a digital filter and then is returned to an analog audio signal by a 1-bit .DELTA..SIGMA. modulation D/A converter. In this system, some calculation error is generated during the passage of data via the digital filter to consequently cause deterioration of the sound quality.
Although a variety of package media are existent with diverse development of CD media inclusive of CD-DA, the current situation relative to common use of data and interchangeability thereof is considered unsatisfactory.